1. Field of the Invention
The field of this disclosure relates to methods and systems for maintaining visual orientation relative to a point of interest and to a rangefinding GPS system for implementing such methods advantageously and strategically during wilderness maneuvers.
2. Description of Related Art
Navigating to a position of interest after having lost visual contact with your destination has long been a problem. While maps and compasses are well-known and very old technology, following a compass on a cross-country course once the way becomes obstructed by trees, fences, etc., requires a great deal of skill and practice.
For example, if you find yourself in an unfamiliar wilderness setting and must walk to some (previously) visually acquired distant point, it is quite easy to lose your way, even for experienced outdoorsmen. Unavoidably, as you move, the surroundings change and direct visual contact with your destination is obstructed, as well as original landmarks and other visual points of reference. Before long, you can no longer see the point of interest (POI) to which you plan to travel, and begin to lose most or all visually guiding mechanisms, becoming increasingly disoriented to your path. If unable to regain your bearings, you must walk back to the original vantage point and re-scout the surroundings, costing much time and effort. There are countless scenarios, particularly for military, hunters, biologists, and other outdoor enthusiasts, for whom this type of disorientation frequently occurs, to the great disadvantage of their objective.
It is possible to use a position-measuring and navigation device such as a Global Positioning System (GPS) receiver to determine where you are when you start navigation, and it is possible to set in a destination point in the GPS if you know the destination by its geographical coordinates (latitude/longitude) or some identifying information such as a name or address (assuming the GPS has such names or addresses in a database). Some devices allow entering the location of a destination by specifying a horizontal offset from a known location—for example, aviation GPS units commonly allow specifying a point as “8 miles on a bearing of 135° from the Ithaca airport” or the like. However, these methods are not of much use in navigating from a known start point to a visual POI, as it is not possible in prior-art navigation systems to set in a destination visually by pointing at something and specifying, “I wish to go there.”
Determining the bearing and distance to a visual POI has been done by traditional surveying techniques. For example, tripod mounted surveying instruments such as transits and inclinometers could be used to measure bearing and elevation angle. Cross-bearings could be taken from two known locations, and calculations done to triangulate a POI. However, the weight and bulk of such devices make them unsuitable for assisting outdoorsmen who require minimal weight and bulk specifications of their equipment—otherwise their goals are compromised, if not made impossible—and even knowing that your POI is on a bearing of 135° horizontally (or magnetic) and 10° up would not help much once you left your starting point.
Rangefinding binoculars exist, such as those manufactured by Zeiss, Bushnell or Leupold. These use lasers to determine range to a point and, in some cases, inclination. They are very expensive, and are marketed to hunters so that they can correct their rifles for distance. Further, knowing the range and inclination from your starting point to the POI does not help much with navigation once you leave the starting point and lose sight of the destination in the woods.
Ballistic algorithms are also seen in a more advanced version of this technology, which calculate a ballistic trajectory rather than only a distance, both of which are displayed in the device's optoelectronic viewfinder. U.S. Pat. No. 7,690,145 “Ballistic Ranging Methods And Systems For Inclined Shooting” describes a method for shooting a projectile weapon by determining the inclination of a line of sight from a vantage point to a target and a line-of-sight range to the target, then predicting a trajectory parameter at the line-of-sight range, for a preselected projectile.
While a combination of prior art technology could be used to precisely locate a POI—at a minimum, this would require a range finding binocular, a handheld GPS, a mobile calculating device, and a compass with aiming device, along with a great deal of complex mathematics and knowledge on the part of the user. Once done, the process, if it is to achieve a high level of accuracy, is imprecise, impractical, extremely time consuming, and involves multiple devices which must be interchanged, and possibly unpacked and repacked in the user's gear.
Relevant U.S. patents to the field include the following:
U.S. Pat. No. 5,825,480 “Observing Apparatus”, superimposes topographic maps in a visual display which obstructs the vision of the user. The method requires topographic information to determine and display a POI. In areas or situations where said topographic information is scarce or inaccurate, the method fails in desired accuracy.
U.S. Pat. No. 6,233,094 “Telescope Utilizing Global Positioning System (GPS)”, calculates a vector between two devices and does not extrapolate POI coordinates. An external device must physically travel to the spot and record its coordinates before the device may be functional. This invention can only orient a user to a location first provided to it from an outside source.
U.S. Pat. No. 7,107,179 “Passive Target Data Acquisition Method And System” transmits targeting information to remote command centers and weapons systems.
U.S. Pat. No. 7,271,954 “Binoculars With An Integrated Laser Rangefinder” is directed primarily to the mechanical details of combining binoculars with a laser rangefinder. The '954 patent mentions including “further electronic measuring devices” such as a GPS, inclinometer, altimeter or compass in the binocular battery compartment, but does not teach or suggest using such devices in combination with the laser rangefinder to provide land navigation to a POI.
U.S. Pat. No. 7,643,054 “Directed Guidance Of Viewing Devices”, is intended for use in something like a guided tour, where a multitude of devices are synced to known locations. This system requires preprogrammed and known points in order to operate, and its lack of improvisational capabilities make it unsuitable for a wilderness setting.
U.S. Pat. No. 7,908,083 “System And Method For Recording A Note With Location Information Derived From Rangefinding And/Or Observer Position”, can be used in the field to determine the location of a distant point and record its coordinates along with user inputted “notes” of information to later be pulled from the device and analyzed on a computer. This invention can display the distance and bearing to the desired POI at the point where it is first used. However it requires that a direct line of sight be established in order to do so. After the user has moved and potentially maneuvered with respect to a recorded POI, if the user no longer has direct visual contact with the POI, the user cannot use this method to orient themselves.